Spamassassin Server

We have spamassassin installed on a server. Zimbra is installed on this same server. Since zimbra has spamassassin built-in, can we remove the installed spamassassin safely or can we configure zimbra to talk to the SA? From what i have read, you can't do that. We also have ClamAV installed on this same server; we can now uninstall clamav too?
How configurable is the built-in spamassassin? In other words, we had some SA plugins installed; can we install these same plugins into the built-in zimbra SA?